Question

Where does megasporogenesis occur in the ovule of an angiosperm? Describe the process up to the development of a mature embryo sac.

Answer 1

Megasporogenesis occurs in the nucellus (in the direction of the micropylar end).

The meiotic division of a single megaspore mother cell (MMC) produces four megaspores, one of which is functional and the other three degenerate. This type of megasporogenesis is monosporic, and the nucleus of the functional megaspore separates mitotically to form the embryo sac's eight nucleate stages. Cell walls envelop six of the eight nuclei, leaving two polar nuclei unaffected. Three cells at the chalazal end of the giant central cell are known as the antipodals, whereas two synergids and one egg cell are located towards the micropylar end.

When fully grown, an angiosperm embryo sac typically has seven cells and eight nuclei.